USGS Climate Data Records (CDRs) are long-term, consistently processed data sets consisting of geophysical parameters derived from Landsat data. The USGS is responsible for producing Surface Reflectance and Land Surface Temperature data as standalone CDRs that will serve as input to higher-level Essential Climate Variables (ECVs) such as Fire Disturbance, Surface Water Extent, Snow Covered Area, and Global Land Cover.
Surface reflectance is the fraction of incoming solar radiation that is reflected from Earth's surface to the Landsat sensor. Interaction with aerosols and gases in the atmosphere can significantly distort the light incident on the satellite sensor, both on the way down through the atmosphere to Earth's surface, and again on the way back up to the sensor. Surface Reflectance images approximate what would be measured by a sensor held just above Earth's surface, corrected to remove artifacts from the atmosphere or illumination and viewing geometry. Surface Reflectance is the most basic remotely sensed surface parameter in the solar reflective wavelengths (visible and infrared), providing the primary input for essentially all higher-level surface geophysical parameters.
Land surface temperature is a measure of how much heat is radiated from Earth's surface. From a satellite's point of view, the surface is whatever the sensor "sees" when it looks through the atmosphere to the ground, including bare earth, snow and ice cover, vegetation (such as leaves on trees), the roofs of buildings, concrete parking lots, and the water of lakes and rivers. Scientists monitor land surface temperature because the warmth rising off Earth's landscapes influences (and is influenced by) global weather and climate patterns, and indicates changes in land-use patterns such as building of cities or agricultural modification of lands.